gif problems in -STABLE

Dimitry Andric dimitry at
Sat Dec 30 09:13:11 PST 2006

Henrik Brix Andersen wrote:
> On Sat, Dec 30, 2006 at 02:56:35AM +0100, Dimitry Andric wrote:
>> For some reason, the ifconfig command now fails to create the proper
>> routing table entries.  With the 2006-11-03 kernel, if I configure my
>> gif0 tunnel as follows:
>> ifconfig gif0 create
>> ifconfig gif0
>> ifconfig gif0 inet6 2001:7b8:2ff:146::2 2001:7b8:2ff:146::1 prefixlen 128
>> route add -inet6 default 2001:7b8:2ff:146::1
> Apart from the two IPv4 endpoint addresses you also assign two IPv6
> addresses with prefixlen 128 to the gif0 interface? Looks weird to
> me...

This is the syntax my IPv6 ISP ( specifies, here:

If you Google around for IPv6 gif tunnel setup information, you'll see
this particular syntax many times.  It used to work for several years,
but if someone can point out an obvious error in it, please let me
know. :)

There's also a similar syntax in the FreeBSD handbook, though it doesn't
mention the prefixlen at all:

Moreover, the syntax mentioned in the handbook doesn't even work:

# ifconfig gif0 create
# ifconfig gif0
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
# ifconfig gif0 tunnel
# ifconfig gif0 inet6 alias 2001:7b8:2ff:146::2 2001:7b8:2ff:146::1
ifconfig: ioctl (SIOCAIFADDR): Invalid argument

The particular thing that I observe, is that when you configured the
gif tunnel with:

ifconfig gif0 inet6 2001:7b8:2ff:146::2 2001:7b8:2ff:146::1 prefixlen 128 

the kernel *used* to automagically create two routing table entries:

2001:7b8:2ff:146::1               link#6                        UHL        gif0
2001:7b8:2ff:146::2               link#6                        UHL         lo0

but as of some date between 2006-11-03 and 2006-12-29, this behaviour
changed, and it now only creates *one* routing table entry:

2001:7b8:2ff:146::2               link#6                        UHL         lo0

And I'm only asking why this was changed.

> Try this configuration in /etc/rc.conf instead:
> ipv6_defaultrouter="2001:7b8:2ff:146::1"
> gif_interfaces="gif0"
> gifconfig_gif0=""
> ipv6_ifconfig_gif0="2001:7b8:2ff:146::2 prefixlen 127"

Doesn't work for me; if I specify prefixlen 127 instead of 126, I get:

ping6: UDP connect: No route to host

when trying to ping the other endpoint of the tunnel, and the required
routing table entry is *not* present:

Destination                       Gateway                       Flags      Netif Expire
::/96                             ::1                           UGRS        lo0
::1                               ::1                           UHL         lo0
::ffff:                 ::1                           UGRS        lo0
2001:7b8:2ff:146::2               link#6                        UHL         lo0 =>
2001:7b8:2ff:146::2/127           link#6                        UC         gif0

In my case, the 2001:7b8:2ff:146::2/127 route is also not enough to
reach 2001:7b8:2ff:146::1; you really have to use a prefixlen of 126 for


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